Brush holder for dynamoelectric machines



Dec. 3, 1946. w. c. EDMUNDSON BRUSH HOLDER FOR DYNAMOELECTRIC MACHINES 7 Filed May 15, 194.4

l N V E N T O R [11 7/2572 [3 fiiizzmisalz B Y Patented Dec. 3, 1946 BRUSH HOLDER FOR DXNAMOELECT-RIC. MACHINES" William C. Edmundson, Anderson, Ind assignor to General Motors Corporation, Detroit,.Mich., a oorporation of Delaware Application.May 13, 1944, Serial No; 535,483

3 Claims. (Cl..17.1--324c) Thisinvention relatesto'brush rigging holders and; more particularly to brush holders for'electric unitshaving a rotatable part;

"An object of the. present' invention isto providea structurewhich not onlyholds' two standard Width brushes firmlyin a receptacle but also allows the brushes to be fed gradually and evenly through the receptacle and against the commulater as the ends of" the brushes are wornaway;

Another'object of the-invention is to provide a brush holder for a plurality of brushes which is sov designed that attention or manual'a'djustment ofthebrush'es is entirel'yeliminateduntil' the useful" lengths have been utilized and the replacement'of the brushes is'n'ecessary.

Another. object' of' the invention is to provide a'brush holderassembly which is easily attached to 'orremoved as a unit? from an. electrical unit, but allows a part of the unit'to be easily'moved so as to facilitate. replacement. of brushes when necessary while theunit is attached; thus elimihating the necessity 'ofremoving'the brush holder assemblyfromthe"electricalunit;

Further objects and advantages of the present invention-will be'apparent from the following descriptionreference being hadto the accompanying drawing'whereirrthe preferred embodiment of the present invention is-clearly shown.

Inthe drawing:

Fig: 1' is a planview of a: brush holder embodyingthepresentinvention: Fig. 2 is a sectional view taken onthe line 2'-2-'- of Fig; 1' and showing a fragmentof a housi'ng in dot and-dashlines.

Fig; 3 isa view lookinginthe direction of arrow 3 in Fig; 2.

Figs; 4 and Bare plan'and'side views, respectively', ofa brush frame utilized in the'present invention,

' Fig. fi'isaplan view'ofaspacer.

Figs. 7 and 8 are plan an'd'front views of a stop member used in-the-presentinvention.

Figs. and 10 are side and planviews respectivelyof" an arm used inthe present invention.

Referring toFig: 2" a fragment ofa casing 20 ofarr electric unit (motor or'generator) is shown. 'A' commuta-tor for the unit is designated by the reference-character 2|. The elements 20- and- 2| are-indicatedbydot-anddash lines.

The electrical circuits and connections are not shown or described in the'present invention in view'of the fact they will" be readily understood 'by'tho'seskilledin the art. Thecircuits or connections; are not necessarily any different from the invention"disclosedherein.

As is well known a motor or generate; is -prorvided With current-carrying brushes to conduct current. Referring toFigs. 1 and 2- the brush holder assembly embodyin the present invention supports and guides a plurality of carbon brushes 22 which are arranged side by side to=en.- gage the outer periphery of the commutator which, in this instance, is extra wide. These blushes are slidably guided in a, brush holder assembly indicated generally by the numeral 25. The brush holder assembly is fixed to the-casing 2!) by screws 25.

The brush holder assembly 25- comprises-a plurality of members punched fromflat sheet metal and then bent bydies to the desired formations. One of the members comprises a U-shaped' frame member 21 including side arms 28 and a yoke 29. The arms 28 are deformed or offset from their normal planes, as at 33, to-provide opposed channels 3| and 32. The webora bottom wall'of channel 3 l is extended. and bent outwardly to form an ear or support 33 for a conducting strap, not shown. The ear 33 is provided with a tapped opening to receive a screw for clamping anonducting strap upon the ear; The free end of each arm is also extended' and bent outwardly to pro.- vide ears 34 by which the frame member is mounted in positionto the casing 20. The yoke 29 is cut away at its upper edge to form notches 35 to-form a lug 3'5 intermediate-the length of-the yoke.

A lever stop 31 may be formed as illustrated in Figs. 7 and 8. This stop comprises wings 38 which are so spaced that they will straddle the arms 28 and the wings are secured to the arms 28; in: any suitablemanner, for example, spot welding. The upper edge of the yoke of lever stop is cut away to provide stops 39 disposed on opposite sides of an extension or lug 48. When the lever stop 3'! is secured in position thestops 39'will be opposite the notches 35 or yoke 29 and lug 40 will be onposite the lu 36. The yoke of the lever stop is spaced a substantial distance from the yoke 29 andextends across from one. arm 28 to the other in parallelism with the yoke. 29 to form a box.- like. or an elongated or rectangular receptacle. This receptacle is preferably divided by a. spacer 4| provided with tangs Ma. on opposite edges thereof which project through aligned openings formed in the lugs 36 and. 40. When the wings 38 are secured to arms 28- of. the member 21', the spacer M is securely held in position with respect to the members 21 and 31. The tangs 41a on'both sides of the spacer 4| are staked and spot welded to their'respective members.

equally.

Rotatably secured between the arms 28 to pivot on studs 50 is a lever 5| which has a pair of spaced fingers 52 extending from one side thereof, said fingers extend over the stops 39 and into the rectangular receptacle. When brushes are on opposite sides of the spacer 4| each arm engages the top surface of a brush 22 which isslidably supported in the rectangular receptacle. The lever 5| is actuated by a pair of springs 69, each spring having one end hooked IOI over an eye in the lever while the other end is hooked over two lugs provided by a spring supfingers are moved in a counterclockwise direction against the action of springs 60 until the free end of the fingers is passed the inner yoke 31 to permit easy removal of the worn brushes and new brushes to be inserted in the receptacle. Thus, the necessity of detaching any part of the brush holder assembly to replace the. brushes is eliminated. e Y

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the port Bl attached to the ears 34 by spot welding. Any desired number of springs or tension-mem-.

bers may be used and it is preferable that there should be at least one for each brush if more than one brush is used. The springs 60 operate to rotate the lever in a clockwise direction as viewed in Fig. 2. Due to the tendency. of the lever 5| to rotate in a clockwise direction, as viewed in Fig. 2, the fingers 52 engage the tops of the brushes to exert aradial pressure on the brushes so as to press them firmly against the wide commutator 2| and the brushes can move to and from the commutator relative to each other. As the brushes wear off the fingers gradually, move in a clockwise direction until one or both of the fingers engage their respective stops 39 whereby further movement of the brush by thefinger is prevented. In this way proper engagement of all the brushes with the commutator surface can be assured anddisengagement off-"all the-brushes from the surface can be avoidied. :Since the brushes are capable of moving relative to each other it is important that the brushes are prevented from chattering.

Furthermore, it also is important that the brushes are moved toward the commutator so that the wear to the brushes is equalized. This is accomplished by the lever 5! with its spaced fin ers 52'which is sturdy enough to apply greater pressure to a longer brush, but flexible enough to apply this pressure dilferentially. Thus, when one of the two brushes, in a receptacle is longer than the other, the longer brush will receive the greater pressure and consequently take the greater proportion of the load current. When this action occurs the longer brush will wear more rapidly. This wear of the longer brush will continue until its length is such as to equalize the pressure and the load between the two brushes.

- One. important advantage of the, construction is to correct unequal wear of brushes in a heavily loaded generator when an unequal heat distribution is present. The present invention continuously corrects unequalized wear of the brushes by the action of the lever as described andthe useful lives of the brushes: are prolonged. It has been found that such action of the. lever extendsthe useful life of a brush, not in the ratio of just two toone, but five or. ten to one, since the brush, in the usual instance of independent brush fingers, which. first assumes'the greater portion of. the load will heat up enough to continue to carry. the greaterload. This will result in rapid wear tov destruction; since the claims which follow.

, What is claimed is as follows:

1. A brush holder assembly for a dynamo electric machine having a frame and a commutator comprising in combination; a pair of sheet metal stampings having a yoke and branches attached thereto, one of said stampings having long branches while the other has short branches, said short branches being hooked under the long branches and secured thereto in a manner so that the yokes are spaced apart to form an elongated opening; a plurality of brushes slidably mounted in the opening and capable of moving relative to each other; ears secured to the long branches at'their free ends; a cross-piece attached to the long branches; a lever pivotally mounted to the long branches and beyond the yokes, said lever including fingers extending above the yoke nearest the pivotal point of the lever and into the opening; spring means having one end anchored to the cross-piece and having the other end attached to the lever to'move the lever in one direction urging the fingers into engagement with respective brushes to move same against the commutator; and means for attaching the ears to the frame to hold the brush holder assembly in a fixed relation relative to the commutator.

2. A brush holder assembly for an electric motor having a frame and a rotating part, comprising in combination; a pair of sheet metal stampings having a yoke and branches attached thereto, one of the stampings having long branches deformed to provide opposed channels, while the other stamping has short branches which are formed to hook under the long branches so that its yoke will close the gap between the channels of the long branches to provide an elongated opening; means for securing two branches together; means attached to the yokes for dividing the opening into a plurality of brush receiving sockets; a brush mounted in each pocket; a crosspiece attached to the long branches beyond the yokes; a lever pivotally mounted to the long branches beyond the yokes; said lever including integral fingers extending above the yoke nearest the pivoted point of the lever and into respective pockets, said lever characterized by the fact that the lever is rigid enough to apply greater pressure to the brush that is longer than another but flexible enough to apply the pressuredifferentially; spring means having one end anchored 5 to the cross-piece and having the other end atthe longer branches to the frame of the motor.

3. A brush holder'assembly for adynamo elec trio machine having a frame and a commutator comprising in combination; a pair of sheet'met al stampings having a yoke and brancheslattached thereto, one of said stampingshaving its branches straddling the branches of the other stamping and secured in a manner that the yokes are spaced apart to form an elongated opening; a plurality of brushes slidably mounted in the opening and capable of moving relative to each other; ears provided by one of the stampings; means cooperating with the ears for securing the stampings to the frame; a sheet metal lever pivotally mounted on the branches of one stamping, said lever including a plurality of fingers, one for each brush; means provided by one of the 6 yokes cooperating with the fingers to limit the movement of the lever toward the commutator when one of the brushes has been worn a predetermined amount; and means for biasing the lever in one direction causing the fingers to abut their respective brushes to move same against the commutator and thus hold the brushes in the opening and allowing ready removal of the brushes from the opening when the lever is ro- WILLIAM C. EDMUNDSON. 

